A method and apparatus for controlling an electromagnetic switching member are known from German Patent No. DE-OS 34 26 799 and from its corresponding U.S. Pat. No. 4,653,447. There, a method and an apparatus are described for controlling a solenoid valve that controls the fuel quantity to be injected into a diesel internal combustion engine. The solenoid valve comprises an excitation winding and a movable armature. To move the armature, a current and/or a voltage is applied to the excitation winding. Within a time window that is defined by a first value and a second value, the current characteristic and/or the voltage characteristic is evaluated in order to detect the time point at which the armature reaches its new limit position.
The time point at which the armature reaches its new limit position has a great influence on the accuracy of the fuel metering. For this reason, this time point must be reliably detected and distinguished from interference signals. With an excessively large time window, interference signals can be interpreted as the switching time point. With an excessively small time window, the switching time point does not lie within the time window in all operating states.